Originally Posted by
EatMyA**
WOW alot of interesting info here but I think some missed the mark, and most didnt even answer the question.
Q: why did centerpulls give way to sidepulls?
A: Because the tire clearances changed.
Centerpulls are a form of cantilever brake exept it is only one piece ("caliper" or whatever) the longer the reach the better they work. They have more "mechanical advantage" (what a confusing term). they just work better when they are longer.
Sidepulls work better when there is less clearance. And honestly, nowadays the clearance is so small, its hard to find a bike that you fit a freaking set of decent fenders. You have to buy some speacially desinged Mickey Moused fender-like creation to have fenders. Heck they even have those stupid "seatpost clamp-on fenders".
....OK rant over sorry.
This is not quite right.
No brakes work better when reach is longer. Mechanical advantage (AKA leverage) is the ratio between the length of the arm on the cable side of the pivot and the length of the arm on the brake shoe side of the pivot. Brakes that are mounted on the brake bridge or fork crown require longer arms on the brake shoe side for greater clearance, and therefore have poorer mechanical advantage with more clearance.
The real advantage of cantilevers is that the leverage is the same no matter how much clearance there is -- the geometry of the brake does not change because it just mounted in a different place.
Regular sidepulls have poorer mechanical advantage than centerpulls. This is not a problem with tight clearance, and good sidepulls work great in this application. There have also been some very nice centerpulls made for racing bikes(Gran Compe, Zeus, others, as well as MAFAC). But with older hardware, centerpulls work better than sidepulls on bikes that have room for fenders and bigger tires.
The disadvantage with sidepulls and cantilevers is that half of the force generated when you pull on the brake lever is wasted because the cable housing just pushes against the cable stop. With sidepulls, this reaction force is used to move one of the brake arms. Leverage is still better with centerpulls over conventional sidepulls at longer reaches, but the dual-pivot sidepull design actually capures the best of both.
That said, I don't own a bike that uses dual pivot brakes, but I have cantilevers, centerpulls, and sidepulls, and they all work fine on the appropriate bikes.